Deck Board Calculator
Estimate linear feet of decking needed from deck area, board width, and gap spacing.
Linear feet to order
How deck board linear footage is calculated
Deck boards don't butt tightly together — a small gap is left between each board for drainage and to allow for seasonal wood movement. That gap means each board effectively "covers" slightly more deck area than its own width, so the calculation has to account for the gap, not just the board width, when converting square footage into linear footage of decking to buy.
The calculator first finds the effective coverage width in feet: (board width + gap) ÷ 12. Dividing your total deck area by that effective width gives the total linear feet of decking required to cover the deck at that spacing.
A waste allowance is then added on top to cover trimmed ends, boards cut around posts or angled deck edges, and the occasional defective board rejected during installation. Ten percent is a reasonable default for a simple rectangular deck; angled or multi-level decks typically need more.
Where these numbers come from
The formula and default values in this calculator are based on:
- Deck board coverage method (effective width including gap spacing) follows standard decking material take-off practice used by decking manufacturers' installation and estimating guides.
These are planning estimates. Check your local building code, product specifications, and a licensed contractor before you buy materials or build.
Frequently asked questions
What gap should I leave between deck boards?
For kiln-dried, dry-installed wood decking, 3/16 inch (about 0.1875 in) is a common standard gap. Wet or green pressure-treated lumber that will shrink as it dries is sometimes installed closer, and composite decking often has its own manufacturer-specified gap, so check the product's install guide.
Does board width mean nominal or actual width?
Use the actual width of the board face after milling, not the nominal size. A "1x6" deck board is typically about 5.5 inches wide in actual face width, and using the nominal 6 inches will slightly undercount the linear footage you need.
How do I handle a diagonal decking pattern?
Diagonal patterns create more angled cuts and off-cuts at the deck perimeter, so increase your waste allowance -- 15-20% is a common adjustment for a 45-degree diagonal layout compared to a straight run pattern.
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